It uses content generated by other players not so that your computer doesn't have to do the work, but so that the game uses content from other players. Lots of user-generated content makes games several orders of magnitude better. Just look at SE4 mods if you don't believe me.
One thing I'd like to know is, he is talking about making the program so that you only need a small amount of code to represent your creatures. Just how much of a system would you need to run it?